1. Field of the Invention
This invention relates to lubricating oil compositions comprising minor amounts of a metal deactivator. More particularly, this invention relates to lubricating oil compositions for use in medium speed diesel engines, which compositions contain a reaction product that is rich in alkyl bis-3-amino-1,2,4-triazole.
2. Description of the Prior Art
Lubricating oil compositions for use in diesel engines are well known. Such compositions will contain one or more additives to improve their properties, e.g., additives which serve as anti-oxidants or corrosion inhibitors and additives which serve as metal deactivators.
Among the various types of diesel engines are the medium speed diesel engines, which are employed as stationary power sources, as marine diesel engines, e.g., engines used on river tow boats, and railroad locomotive engines. Particularly important are the medium speed railroad locomotive engines.
A number of lubricant additives are especially useful in lubricating oils to prevent sulfur induced corrosion of copper and copper alloys. For example, a highly effective metal passivator for use in lubricating oils that can be employed as crankcase oils for gasoline or diesel engines is the product of a reaction of 2,5-dimercapto-1,3,4-thiadiazole, sulfur dichloride, and an olefin containing 6 to 30 carbon atoms, as described by Lam in U.S. Pat. No. 4,487,706. Another example is a reaction product of a hydrocarbyl succinic anhydride in which the hydrocarbyl radical has from 12 to 30 carbon atoms and 5-amino triazole, as discussed by Sing, et al., in U.S. Pat. No. 4,256,595.
In U.S. Pat. Nos. 3,272,746 and 3,341,542, Le Seur, et al., disclose lubricating oil compositions containing acylated nitrogen compounds prepared, for example, by reacting a substituted succinic acid or derivative thereof with a nitrogen-containing compound, such as ammonia, aliphatic amines, aromatic amines, heterocyclic amines, or carboxylic amines. The resulting detergent composition comprises an oil-soluble, acylated nitrogen composition characterized by the presence within its structure of (A) a substantially hydrocarbon-substituted polar group selected from the class consisting of acyl, acylimidoyl, and acyloxy radicals wherein the substantially hydrocarbon substituent contains at least about 50 aliphatic carbon atoms and (B) a nitrogen-containing group characterized by a nitrogen atom attached directly to said relatively polar group. In Example 38 of these patents, polyisobutene-substituted succinic anhydride, aminoguanidine bicarbonate, and mineral oil were mixed and heated at a temperature of 130.degree. C. (266.degree. F.) to 165.degree. C. (329.degree. F.) for 5 hours. The residue was mixed with mineral oil and heated to 150.degree. C. (302.degree. F.) and filtered. The resulting product was used as a lubricating oil additive and found to be an effective dispersant. These patents teach that the mixture of acid-producing compound and the nitrogen-containing reactant is usually heated at a temperature above about 80.degree. C. (176.degree. F.), preferably, within the range of about 100.degree. C. (212.degree. F.) to about 250.degree. C. (482.degree. F.). These patents teach that guanidines are included in sources of nitrogen-containing compounds and present, as examples, guanidine, 1,3-diphenylguanidine, and 1,2,3-tributylguanidine. These patents do not indicate that the resulting product comprises triazoles. Furthermore, there is no suggestion that the product would be a suitable metal deactivator in an engine lubricant oil composition.
In U.S. Pat. No. 4,491,527, Lange, et al., disclose ester-heterocycle compositions useful as "lead paint" inhibitors and lubricants, e.g., compositions comprising a major proportion of a pentaerythritol ester of an alkenyl succinic acid in which the alkenyl group contains at least about 30 carbon atoms and a minor proportion of a heterocyclic condensation product of said alkenyl succinic acid derived from a 5-membered ring heterocycle containing at least 2 ring hetero atoms separated by a single carbon atom, at least one of said hetero atoms being nitrogen. The heterocyclic condensation product is characterized by the presence of at least one heterocyclic moiety including a 5- or 6-membered ring which contains at least 2 ring hetero atoms, separated by a single carbon atom. Such ring hetero atoms may be oxygen, sulfur, and nitrogen, with at least one thereof being nitrogen. Most often, the heterocyclic moiety contains a maximum of three ring hetero atoms and a 5-membered ring, preferably, a triazole or thiadiazole ring, and, most desirably, a 1,2,4-triazole ring. This patent teaches that aminoguanidine and salts of aminoguandine, such as aminoguanidine bicarbonate, are examples of acylic heterocycle precursors which may be reacted with the proper acid or acid derivative group. This patent does not suggest that a reaction product rich in an alkyl-substituted bis-3-amino-1,2,4-triazole would be a suitable metal deactivator in a medium speed diesel engine lubricating oil composition.
It has now been found that a reaction product of an alkyl-substituted dicarboxylic acid compound, e.g., a polybutenyl succinic anhydride, and a basic salt of amino-guanidine, e.g., aminoguanidine bicarbonate, which product comprises alkyl bis-3-amino-1,2,4-triazole, can be used in medium speed diesel engine oils, particularly, railroad locomotive diesel engine oils, protect metal engine parts, particularly, the copper and copper alloy parts.
According to the present invention, there is provided a lubricating oil composition for use in medium speed diesel engines, which composition provides reduced corrosion of metal engine parts and which composition comprises a major proportion of an oil of lubricating viscosity, particularly, a mid-range viscosity index (MVI) base oil, and a minor (metal deactivating) amount of a metal deactivator-dispersant that is rich in alkyl bis-3-amino-1-2,4-triazole. A suitable alkyl bis-3-amino-1,2,4-triazole is polybutenyl bis-3-amino-1,2,4-triazole. Typically, the metal deactivator-dispersant additive is present in an amount within the range of about 0.001 wt % to about 10 wt % based on the weight of the lubricating oil composition.